1. Field of the Invention
The present invention relates to a Mn-Zn single crystalline ferrite head for use in magnetic tape recording and reproducing apparatus and to a method of making the same.
2. Description of the Prior Art
It is widely known that single crystalline ferrites, in particular Mn-Zn single crystalline ferrites, are desirably used as the magnetic core materials of the magnetic heads for magnetic tape recording and reproducing apparatus such as audio and video tape recorders, due to the reason that the single crystalline ferrites have the advantages of very high wear resistance and of superior magnetic properties, such as saturation magnetization, coercive force and permeability, and superior high frequency characteristics in comparison with alloyed materials, such as Permalloy and Sendust. However, such single crystalline ferrite heads inherently have a drawback in that they generate characteristic noise which is caused by rubbing against a magnetic tape, i.e. "ferrite noise". This ferrite noise occurs when the single crystalline ferrite heads are used in contact with a running magnetic tape and thereby results in a deterioration of the signal-to-noise ratio particularly in a reproduction mode of the apparatus.
In order to avoid the above described disadvantage of the ferrite noise inherent in the single crystalline ferrite heads, it has been proposed, for instance, as disclosed in Canadian Pat. No. 949,777 and a technical report entitled "Low Noise Manganese-Zinc Single Crystal Ferrite Heads" by Hisashi Watanabe, one of the inventors of the present invention, et al., which appeared on pages 497 through 500, of IEEE TRANSACTION ON MAGNETICS, Vol. Mag. 8, No. 3 for September 1972, to provide low noise Mn-Zn single crystalline ferrite heads. The above recited Canadian Pat. No. 949,777 and the technical report disclose that the ferrite noise generated in the Mn-Zn single crystalline ferrite heads is markedly reduced by dispersedly precipitating different phase such as SnO.sub.2 phases in the Mn-Zn single crystalline ferrites so that pseudo grains, each diameter of which is less than 30 .mu.m, are formed in the crystal. In this connection, reference may be made to a technical report entitled "Growth and Properties of Manganese Zinc Tin Ferrite Single Crystals" also by H. Watanabe et al., which appeared on pages C1-51 through C1-55, of JOURNAL DE PHYSIQUE, Vol. 38 for April 1977 and Japanese Pat. No. 894,305 (Publication No. SHO 52-24,998) and Japanese Pat. No. 894,306 (Publication No. SHO 52-24,999), wherein there is described in detail a method for precipitating the desired quantity of the different phases of SnO.sub.2 in the Mn-Zn single crystalline ferrites.
Although the drawback of the ferrite noise inherent in the Mn-Zn single crystalline ferrite head was solved by precipitation of the different phases, such as SnO.sub.2, phases into the ferrite crystal as described above, another problem has arisen from such precipitation in that the output of the head is reduced by the virtue of the fact that the effective permeability in the magnetic path of the head core is lowered by the different phases which are homogeneously precipitated in the whole magnetic path of the head core. However, the Mn-Zn single crystalline ferrites in which the different phases are homogeneously precipitated have been widely used as the magnetic head core material, since such low noise Mn-Zn single crystalline ferrite heads are high demand in the field of magnetic tape recording and reproducing even though the permeability of the head core is somewhat sacrified. That is to say, an implicit problem of the permeability in the improved low noise Mn-Zn single crystalline ferrite heads has hithertofor remained unsolved.